The wildfire risk has climbed to the highest level so far, with Valais now under "very high danger" and open fires banned across several cantons.
The warning covers Sion, Sierre, Montana, Fully and other Valais districts, where 30-degree heat and prolonged drought have left forests tinder-dry.
Ticino and Graubünden are historically most exposed, though no canton is entirely safe.
Heat kills more than the roads
Heat now kills more people in Switzerland than road accidents.
Geneva left with the bill after G7
Geneva cantonal minister Carole-Anne Kast says Bern gave in too easily to France over who pays for last month's G7 summit in Évian.
HPV vaccines for all
Switzerland has become the first country in Europe to widen its HPV vaccine to everyone aged 9 to 45, including men up to 45.
Yverdon maps its heat island
With the Plateau facing 35 degrees on Thursday, Yverdon-les-Bains has installed 15 sensors to work out how hot its own streets really get.
Shaqiri meets hundreds of fans in Geneva
Hundreds of football fans packed Geneva's La Praille shopping centre yesterday to meet Swiss star Xherdan Shaqiri.
Elderly deaths rise during the heatwave
Switzerland's June heatwave is being blamed for around 200 additional deaths among people over 65, according to new federal figures.
